Polishing compositions for reduced defectivity and methods of using the same

ABSTRACT

Chemical mechanical polishing compositions include an abrasive, a first removal rate enhancer; and water; wherein the polishing compositions have a value of less than 800,000 for the relation: large particle counts/weight percent abrasive, when measured using a 0.2 μm bin size.

BACKGROUND OF THE DISCLOSURE 1. Field of the Disclosure

The present disclosure relates to chemical-mechanical polishingcompositions. More particularly, the present disclosure relates to suchcompositions that have large particle counts below a desired threshold.

2. Description of the Related Art

Copper is a commonly used material for forming interconnects insemiconductor manufacturing. Once a copper inlaid structure is formedby, for example, a damascene process, the isolated copper wires are madeby polishing and clearing copper and barrier metal between the inlaidwires. Copper and barrier layer CMP involves polishing of copper andbarrier layers. It is desired to polish the wafers at a high removalrate of material to enhance throughput, while still maintainingfavorable wafer characteristics such as a low number of overall defects.

The process known as chemical mechanical polishing or planarization(CMP) involves the polishing/planarization of different layers onsemiconductor wafers using a polishing pad and slurry to polish awayexcess or unwanted layers of materials prior to construction ofsubsequent layers. Copper is a commonly used material for forminginterconnects in semiconductor manufacturing. Once a copper inlaidstructure is formed by, for example, a damascene process which depositscopper according to the pattern dictated by, for example a damasceneprocess, the isolated copper wires are made by polishing and clearingcopper and barrier metal between the inlaid wires.

Copper and barrier layer CMP involves using a polishing slurry ormultiple polishing slurries to remove copper and barrier layers to theextent required to proceed to the next step in the semiconductormanufacturing process. A typical copper CMP process consists of 3process steps. First, the electro-plated copper overburden (which may beup to 5 μm or more in thickness depending on technology node) is rapidlypolished down at a relatively high down force, leaving some amount ofcopper until the deposition topography is fully planarized. Theremaining copper overburden after full planarization during the firststep is polished off at a lower down force, with a stop on the barrierlayer. High removal rates, to increase throughput, combined withplanarization efficiency and low defects are key needs for a CMPprocess. Particularly, undesirable deep scratches from the copper CMPsteps may persist during later stages of chip fabrication if they are ofsufficient depth not to be removed in subsequent barrier polishing.These types of scratches can ultimately compromise device performanceand lead to non-functioning devices and reduced die yield.

CMP processes are similarly used to polish substrates including metalsother than copper and/or dielectric materials (while also possiblyadditionally including copper). Accordingly, improved polishingcompositions and methods of their use are sought after in thesemiconductor industry.

SUMMARY

This summary is provided to introduce a selection of concepts that arefurther described below in the detailed description. This summary is notintended to identify key or essential features of the claimed subjectmatter, nor is it intended to be used as an aid in limiting the scope ofthe claimed subject matter.

In one aspect, embodiments disclosed herein relate to chemicalmechanical polishing compositions that include an abrasive, a firstremoval rate enhancer; and water; wherein the polishing composition hasa value of less than 800,000 for the relation: large particlecounts/weight percent abrasive, when measured using a 0.2 μm bin size.The present disclosure also provides a method of polishing a substratewith the compositions.

In another aspect, embodiments disclosed herein relate to chemicalmechanical polishing compositions that include an abrasive, a firstremoval rate enhancer; and water; wherein the polishing composition hasa value of less than 50,000 for the relation: large particlecounts/weight percent solids, when measured using a 0.2 μm bin size.

In another aspect, the present disclosure provides a method of preparinga polishing composition, wherein the polishing composition comprises anabrasive, a first removal rate enhancer, and water. The polishingcomposition has a value of less than 800,000 for the relation: largeparticle counts/weight percent abrasive, when measured using a 0.2 μmbin size. The method comprises the steps of selecting the abrasive sothat it conforms to the value, and combining the abrasive, the firstremoval rate enhancer, and the water.

Other aspects and advantages of the claimed subject matter will beapparent from the following description and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows LPC counts for an unfiltered slurry of the prior art (inFIGS. 1-13, the “Standard slurry”), and an unfiltered compositionaccording to the present disclosure (in FIGS. 1-13, the “Low-Defectslurry”), using a bin size of 0.56 μm.

FIG. 2 shows LPC counts for an unfiltered slurry of the prior art, andan unfiltered composition according to the present disclosure, using abin size of 1.01 μm.

FIG. 3 shows LPC counts for an unfiltered slurry of the prior art, andan unfiltered composition according to the present disclosure, using abin size of 0.29 μm.

FIG. 4 shows LPC counts for an unfiltered slurry of the prior art, andan unfiltered composition according to the present disclosure, using abin size of 0.2 μm.

FIG. 5 is a plot showing a comparison of the normalized copper removalrate for a prior art slurry and a composition according to the presentdisclosure.

FIG. 6 is a plot showing a comparison of the dishing observed afterpolishing wafers having a variety of Cu patterns (i.e., linewidth/density) using a prior art slurry and a composition according tothe present disclosure.

FIG. 7 shows normalized total defect counts for the composition of thepresent disclosure, as compared to a prior art polishing slurry.

FIG. 8 shows normalized total number of scratches for the composition ofthe present disclosure, as compared to a prior art polishing slurry.

FIG. 9 shows the LPC counts at 0, 3, and 7 days of aging for tenpolishing compositions using a bin size of 0.2 μm.

FIG. 10 shows the LPC counts at 0, 3, and 7 days of aging for tenpolishing compositions using a bin size of 0.29 μm.

FIG. 11 shows the LPC counts at 0, 3, and 7 days of aging for tenpolishing compositions using a bin size of 0.56 μm.

FIG. 12 shows the LPC counts at 0, 3, and 7 days of aging for tenpolishing compositions using a bin size of 1.01 μm.

FIG. 13 shows a plot of the LPC counts, using a 0.2 μm bin size,measured over a period of 11 days for a prior art polishing slurry and acomposition of the present disclosure after they have been subjected toa filtration using a 0.1 μm depth filter.

FIG. 14 shows the LPCs/weight % silica, measured at a 0.2 μm bin size,for Slurries 1-10 at 0, 3, and 7 days after formulation.

FIG. 15 shows the LPCs/weight % silica, measured at a 0.29 μm bin size,for Slurries 1-10 at 0, 3, and 7 days after formulation.

FIG. 16 shows the LPCs/weight % solids, measured at a 0.2 μm bin size,for Slurries 1-10 at 0, 3, and 7 days after formulation.

FIG. 17 shows the LPCs/weight % solids, measured at a 0.29 μm bin size,for Slurries 1-10 at 0, 3, and 7 days after formulation.

DETAILED DESCRIPTION OF THE DISCLOSURE

Embodiments disclosed herein provide chemical mechanical polishingcompositions that are capable of minimizing defects, in particularmicroscratches, when compared to known CMP compositions. Thecompositions of the disclosure include an abrasive with a large particlecount (LPC) that is specifically limited to be below a defined level.The deleterious effects of higher levels of LPCs (e.g., high level ofdefects) are thereby avoided or minimized when employing thecompositions of the disclosure, while still maintaining the same, orhigher, degree of polishing activity.

The compositions of the present disclosure have a large particle count(LPC), which refers to the number of particles greater than a certainsize, below a certain threshold. In the CMP field, a tangiblecorrelation has remained elusive between the LPCs of a composition andthe number of defects (e.g. scratches) on the polished surface. Thepresent inventors have surprisingly discovered that there is a clearimproved result when the number of LPCs of a composition are kept belowa certain amount with respect to the amount of abrasive (or solids) inthe composition.

LPCs in CMP slurries may come from the abrasives used in the slurries,or other components added as solids during slurry formulation that maydissolve over time, but may do so slowly and/or incompletely (e.g.,corrosion inhibitors, removal rate enhancers, etc.). As will beexplained in further detail in this application, the present inventorshave found that scratches or defects may be minimized during polishing,while maintaining the same, or higher, polishing rate, by using apolishing composition that includes less than 800,000 LPCs/weightpercent abrasive (i.e., a value less than 800,000 LPCs for the relation:large particle counts/weight percent abrasive), when LPCs are measuredusing a 0.2 μm bin size (i.e., when LPCs are classified as particleslarger than 0.2 μm). Further, and relatedly, polishing compositions thathave less than 50,000 LPCs/weight percent solids (i.e., a value lessthan 50,000 LPCs for the relation: large particle counts/weight percentof components added as solids during formulation), when LPCs aremeasured using a 0.2 μm bin size, also achieve fewer wafer defects andscratching than compositions having a higher LPC/weight percent solidsreading. Percent solids is intended to be distinct from percentabrasives in that percent solids encompass all components added duringformulation in a solid form, some of which may ultimately dissolve orpartially dissolve upon aging. Standardizing the LPC count to either theweight percent abrasive or weight percent solids allows for directcomparison of compositions regardless of their overall composition asthe inventors have observed that higher scratches are observed for awide variety of compositions (e.g., those with 0.08 wt % to those with10 wt % abrasive) if they have LPC counts outside of the rangesreferenced above.

As discussed in greater detail below, the benefits described in thepresent disclosure were surprising because they did not appear when LPCswere measured using a conventional higher threshold value than thethreshold identified herein. The benefits of the claimed ratio onlyappear when measuring the LPCs using the smaller bin sizes discussedbelow. In addition, it was previously thought that the removal rateenhancers of CMP compositions contributed significantly to LPCs anddefects, but the present disclosure sets forth that the abrasives werethe biggest contributors to scratching defects. This is why the ratio ofthe present disclosure uses a smaller LPC threshold that is moredirected to encompass the abrasive particles in the composition. As isalso discussed below, significant benefits occur when the compositionsmeet the limits of the claimed ratio.

As mentioned above, undesirable deep scratches from the CMP steps maypersist during later stages of chip fabrication if they are ofsufficient depth not to be removed in any subsequent polishing steps.These types of scratches can ultimately compromise device performance,and one of the potential culprits behind deep scratches may be largeundesirable particles present in the CMP slurry. The presence of theseundesirable particles is typically monitored by light scatteringtechniques to determine LPCs, in which the concentrations of particleswith diameters above a selected threshold, conventionally around 0.5micrometers (μm) and/or around 1.0 μm, are quantified in solution. Theconventionally selected size threshold (e.g., 0.5 μm and/or 1.0 μm) istypically well above the 99th percentile for the size distribution ofdesired particles (e.g., abrasives) in solution and thus prohibitsconfusion as to whether or not particles contributing to LPCs inslurries are undesirable (e.g., a contaminant) or desirable. However,the inventors have surprisingly discovered that the portion of theabrasive particles above about 0.2 μm is highly correlated withincreased scratching. Thus, a portion of the abrasive, which is commonlybelieved to be desirable due to the need to achieve satisfactory removalrates and overall polishing performance, is actually detrimental andcontributes significantly to highly undesirable scratching duringpolishing.

As will be demonstrated in the Examples presented later in thisdisclosure, the inventors have discovered that controlling theLPCs/weight percent abrasive to be less than 800,000, when LPCs aremeasured using a 0.2 μm bin size, results in polishing compositions thatachieve reduced wafer defects/scratches when compared with a similarlyformulated polishing composition that has a higher LPC/weight percentabrasive, when LPCs are measured using a 0.2 μm bin size. Without beingbound by theory, the inventors believe that the reduction indefects/scratches is achieved when adhering to the above LPC limit dueto the LPC limit reducing the relative amount of the larger abrasives inthe compositions, which are most likely to create the scratches due totheir hardness and size. Indeed, in the background section of U.S. Pat.No. 9,914,852 it is discussed that particles greater than about 0.5 μmare thought to present potential scratching problems, but there is nomention therein about the importance of limiting particles greater than0.2 μm to reducing defects/scratches during polishing, as isdemonstrated in the present application.

In polishing slurries LPCs are dominated by the abrasives when measuredat a 0.2 μm bin size, whereas the abrasive component is much lessrepresented in measurements using larger bin sizes (e.g., about 0.5 μmand about 1 μm) due to the typical size selections used for theabrasives used in polishing compositions. Abrasives used in polishingcompositions have particle size distributions which may be significantlydifferent depending on the synthesis method or parameters of thesynthesis process even though two different abrasives may have similar,or even the same, average particle size. For example, taking twoabrasive sources each having an average particle size of 60 nm, oneabrasive source may have a broader particle size distribution and alarger proportion of particles that are greater than 200 nm (i.e., abovea 0.2 μm bin size) than the other abrasive source that has a narrowerparticle size distribution. Consequently, the LPCs for the broaderdistribution abrasive source would be higher (and potentially outside ofthe limit referenced in this disclosure) when measured at a 0.2 μm binsize than the narrower distribution abrasive source even though theyhave the same average particle size.

The considerations discussed in the preceding paragraph are one reasonwhy currently available slurries or compositions cannot be assumed topossess the properties of the present disclosure. Current slurries mayhave particle sizes that are similar on average, but again, that doesnot mean that they would have the same LPC counts at the described binsizes. Furthermore, as described earlier in the present specification,there is no indication that there could or would be such a divergence inthe LPC counts of the present compositions as compared to what iscurrently available, since the difference were not at all apparent atlarger bin sizes. The abrasives of the present disclosure should beselected so that they achieve the desired LPC count and ratio. Asestablished earlier in the disclosure, even filtering slurries will notnecessarily mean that the LPCs will be reduced to the threshold levelsof the present disclosure. The abrasives of the present disclosure mayalso be chemically treated to or formed with a particular chemicalsynthesis to ensure that they meet the desired LPC properties.

In practice, a filtration process may be used to attempt to removeparticles larger than a certain size from a product or slurryformulation. However, even the use of filtration may not always beeffective for lowering LPCs to a level where scratches or defects areminimized. For example, and as will be shown in the Examples presentedlater in the disclosure, 0.1 μm depth filters are not effective atreducing the LPCs below the threshold of 800,000 LPCs/weight percentabrasives or 50,000 LPCs/weight percent solids. This is not intuitive asone would expect filters with having a 0.1 μm pore diameter would becapable of significantly reducing the occurrence of particles capable ofcausing counts in the 0.2 μm bin size, which includes particles largerthan 0.2 μm. However, depth filters have a wide distribution of poresizes and allow at least a portion of components larger than the ratedvalue through the filter. Thus, in one or more embodiments, a polishingslurry of the present disclosure is not filtered after formulationand/or the abrasive component used in the polishing slurry is notfiltered before formulation. For example, when abrasives are provided bya supplier they are usually dispersed within a solution which is thenmixed together with the other components to formulate a slurry. Thus, insome embodiments, the dispersed abrasive solution provided by a supplieris not filtered prior to being formulated into a polishing slurry.

In one or more embodiments, the polishing composition includes anabrasive selected from the group consisting of alumina, fumed silica,colloidal silica, coated particles, titania, ceria, zirconia, and anymixtures thereof. In one or more embodiments, the abrasive is selectedfrom the group consisting of fumed silica, colloidal silica, andmixtures thereof.

In one or more embodiments, the polishing composition includes a removalrate enhancer selected from the group consisting of organic acids, andorganic acid salts. In more specific embodiments, the removal rateenhancer is selected from the group consisting of amino acids,carboxylic acids, polyamines, ammonia based compounds, quaternaryammonium compounds, inorganic acids, compounds with both carboxylic andamino functions, ethylenediaminetetraacetic acid, diethylene triaminepentaacetic acid, and any mixtures thereof.

In one or more embodiments, the polishing composition includes acorrosion inhibitor selected from the group consisting of azole, azolederivatives, and mixtures thereof. In more specific embodiments, thecorrosion inhibitor may be selected from the group consisting ofbenzotriazole, benzotriazole derivatives, tolyltriazole, and mixturesthereof.

In one or more embodiments, the polishing composition includes anoxidizer selected from the group consisting of hydrogen peroxide,ammonium persulfate, silver nitrate, ferric nitrates, ferric chloride,per acid, per salts, ozone water, potassium ferricyanide, potassiumdichromate, potassium iodate, potassium bromate, vanadium trioxide,hypochlorous acid, sodium hypochlorite, potassium hypochlorite, calciumhypochlorite, magnesium hypochlorite, ferric nitrate, KMnO₄, otherinorganic or organic peroxides, and any mixtures thereof.

In one or more embodiments, the polishing composition includes at leastone selected from the group consisting of a surfactant, a second removalrate enhancer, a biocide, a surface finisher, a pH adjuster, a defectreduction agent, a dishing reducer, a dynamic surface tension reducer,or any mixtures thereof.

In one or more embodiments, the polishing composition described hereincan be substantially free of one or more of certain ingredients, such assalts (e.g., halide salts), polymers (e.g., cationic or anionicpolymers, or polymers other than a dishing reducing agent), surfactants(e.g., those other than a copper corrosion inhibitor), plasticizers,oxidizing agents, corrosion inhibitors (e.g., non-azole corrosioninhibitors), and/or certain abrasives (e.g., ceria or alumina abrasivesor non-ionic abrasives). The halide salts that can be excluded from thepolishing compositions include alkali metal halides (e.g., sodiumhalides or potassium halides) or ammonium halides (e.g., ammoniumchloride), and can be chlorides, bromides, or iodides. As used herein,an ingredient that is “substantially free” from a polishing compositionrefers to an ingredient that is not intentionally added into thepolishing composition. In some embodiments, the polishing compositionsdescribed herein can have at most about 1000 ppm (e.g., at most about500 ppm, at most about 250 ppm, at most about 100 ppm, at most about 50ppm, at most about 10 ppm, or at most about 1 ppm) of one or more of theabove ingredients that are substantially free from the polishingcompositions. In some embodiments, the polishing compositions describedcan be completely free of one or more the above ingredients.

EXAMPLES

In the examples presented below, the referenced LPC measurements for the0.2 μm, 0.29 μm, 0.56 μm, and 1.01 μm bin sizes were measured over timeusing a Celerity (Tualatin, Oreg.) Slurry Particle Measuring Cart modelAD10300-01 fitted with a Particle Measuring Systems Inc. (Boulder,Colo.) Liquilaz S02 liquid optical particle counter. All samples werediluted within the cart with 0.04 μm filtered deionized water by afactor of 500-1000 in order to bring counts to a level suitable for theS02 particle counter. The reported LPC's take into account all dilutions(FIGS. 1-4). Furthermore, in certain examples the results werenormalized by % Silica loading (FIG. 15 and FIG. 16), as well as by %Solids loading (FIG. 17 and FIG. 18).

Example 1

In this example the variation of the LPC count over a period of elevendays was measured at multiple bin sizes for both a prior art slurry anda composition according to the present disclosure. The prior artpolishing slurry has an LPC count that exceeds the limit taught forpolishing slurries according to the present disclosure. Conversely, thepolishing composition of the present disclosure has an LPC count belowthe limit taught for polishing slurries according to the presentdisclosure. The components of the two polishing slurries were chemicallythe same and used in the same amounts within each composition.

Two types of solid materials may be initially added when formulating apolishing composition. One type is a solid that remains solid in thecomposition, for example an abrasive, and another type of componentwould be a solid that dissolves over a period of time in thecomposition. The solids that remain solid over time would maintain astable presence in the LPC count of a slurry, while the solids thatdissolve would show a decreasing presence on the LPC count of the slurryand also would not pose a concern for scratching a wafer duringpolishing once dissolved. Conventional thinking assumes that largerparticles lead to scratching defects when polishing and therefore LPCvalues are commonly measured and reported using bin sizes of 0.56 μmand/or 1.01 μm. That is, it is common practice to measure LPC counts ofparticles greater than about 0.56 μm and/or 1.01 μm and try to minimizetheir presence in polishing slurries.

FIGS. 1 and 2 show LPC counts for an unfiltered prior art slurry and anunfiltered polishing composition of the present disclosure at bin sizesof 0.56 μm and 1.01 μm, respectively. What these plots show is that theLPC's within these bin sizes for both slurries start out high and thenstabilize at lower and substantially the same values as time progresses.This result indicates that LPC's within the two bin sizes are primarilydominated by components that dissolve over time and not solid abrasivecomponents, which do not dissolve over time. Further, because the valuesstabilize at roughly the same values the Low Defect composition'sability to reduce defects (shown in FIGS. 7 and 8) when compared with aprior art composition is not explained by LPC values in these two sizeranges.

FIG. 3 shows LPC counts for an unfiltered prior art slurry and anunfiltered polishing composition of the present disclosure at a bin sizeof 0.29 μm (i.e., counting particles with a size greater than 0.29 μm).Similar to the results for the 0.56 μm and 1.01 μm bin sizes, theresults in FIG. 3 show that the LPC's within these bin sizes for bothslurries start out high and then stabilize at lower and substantiallythe same values as time progresses. Thus, the particles within this binsize are also dominated by components that dissolve over time and do notexplain the Low Defect composition's ability to reduce defects(discussed later in Example 4 and shown in FIGS. 7 and 8) when comparedwith a prior art composition.

FIG. 4 shows LPC counts for an unfiltered prior art slurry and anunfiltered polishing composition of the present disclosure slurry at abin size of 0.2 μm (i.e., counting particles with a size greater than0.2 μm). Here, the LPC counts for the two different slurries show asignificant divergence. Specifically, the LPC counts remain relativelystable over the time period tested, indicating that the value isdominated primarily by the non-dissolving abrasive component. Secondly,the values obtained for prior art composition are more than double thecount values obtained for the polishing composition of the presentdisclosure. This result, combined with the results discussed later inExample 4 and shown in FIGS. 7 and 8, unexpectedly suggests that byspecifically controlling the amount of particles having a size greaterthan 0.2 μm a reduction in scratches/defects on polished wafers can beachieved.

Example 2

In Example 2 the copper blanket removal rate of a prior art polishingslurry is compared with the copper removal rate of the polishingcomposition of the present disclosure at two different downforce values.The prior art polishing slurry has an LPC count that exceeds the limittaught for polishing slurries according to the present disclosure.Conversely, the polishing composition of the present disclosure has anLPC count below the limit taught for polishing slurries according to thepresent disclosure. The components of the two polishing slurries werechemically the same and used in the same amounts within eachcomposition.

The results presented in FIG. 5 demonstrate that the copper removal ratefor each slurry at each downforce value were comparable within normalwafer-to-wafer process variations.

Example 3

In Example 3 the dishing observed after polishing a wafer with a priorart polishing slurry is compared with the dishing observed afterpolishing with the polishing composition of the present disclosure. Theprior art polishing slurry has an LPC count that exceeds the limittaught for polishing slurries according to the present disclosure.Conversely, the polishing composition of the present disclosure has anLPC count below the limit taught for polishing slurries according to thepresent disclosure. The components of the two polishing slurries usedthe same chemical components within each composition. Further, thepolishing conditions were the same when using each composition.

The results presented in FIG. 6 demonstrate that the amount of dishingobserved is comparable after using the two slurries on wafers having avariety of Cu patterns (i.e., line width/density).

Example 4

In this example the total defects and type of defects found on blanketcopper wafers polished with a prior art polishing slurry were comparedwith those found on blanket copper wafers polished with the polishingcomposition of the present disclosure. The prior art polishing slurryhas an LPC count that exceeds the limit taught for polishing slurriesaccording to the present disclosure. Conversely, the polishingcomposition of the present disclosure has an LPC count below the limittaught for polishing slurries according to the present disclosure. Thecomponents of the two polishing slurries were chemically the same andused in the same amounts within each composition. Further, the polishingconditions were the same when using each composition.

FIG. 7 shows that when the data is normalized the total defect countsfor the polishing composition of the present disclosure aresignificantly lower than those observed when polishing with a prior artpolishing slurry. FIG. 8 shows that when the data are normalized thetotal number of scratches for the polishing composition of the presentdisclosure are significantly lower than those observed when polishingwith a prior art polishing slurry. Further, due to the strongcorrelation in the value obtained in FIG. 8 for the number of scratchesobtained using the polishing composition of the present disclosure andthe value shown in FIG. 7 for the total number of defects (i.e., thenormalized values are similar at around 0.6), it can be concluded thatthe majority of the defects observed on the polished wafers arescratches, and not stains, organic residue, corrosion, etc. The resultsalso show the scratches can be reduced about 40% when polishing with thepolishing composition of the present disclosure.

Example 5

In this example the generality of the LPC count trends depending on binsize selection detailed in Example 1 is demonstrated by showing barplots for ten distinct polishing compositions, each having differingcomponents and/or amounts of components. FIG. 9 shows the LPC counts at0, 3, and 7 days of aging for the ten polishing compositions using a binsize of 0.2 μm. FIG. 10 shows the LPC counts at 0, 3, and 7 days ofaging for the ten polishing compositions using a bin size of 0.29 μm.FIG. 11 shows the LPC counts at 0, 3, and 7 days of aging for the tenpolishing compositions using a bin size of 0.56 μm. FIG. 12 shows theLPC counts at 0, 3, and 7 days of aging for the ten polishingcompositions using a bin size of 1.01 μm. Importantly, the LPC countsshown are normalized by the percent of solids initially added to formeach composition (i.e., all solid components including abrasives and anyother components added as solids during the initial formulation) so thatthe LPC counts may be compared even though each slurry composition isdistinct.

When viewed from the smaller to larger bin sizes (i.e., FIG. 9 to FIG.12) the LPC counts are relatively stable for all of the slurries in FIG.9 (using a 0.2 μm bin size), while the counts decrease significantlyfrom Day 0 to Day 3 for all of the slurries when measured at the threelarger bin sizes as shown in FIGS. 10-12. This evidence bolsters thegenerality of the conclusions discussed in Example 1, where theabrasives were shown to primarily control the LPC counts in the 0.2 μmbin sizes, while the soluble solid components where shown to control theLPC counts in the larger and more conventionally measured bin sizesshown by the significant decrease in LPC counts over time. Further, thedata also presents an explanation for why the conventionally held beliefthat LPC counts should be controlled in the 0.56 μm and/or 1.01 μm binsize has not correlated well with reducing defects/scratches in realworld applications. Specifically, scratches are primarily caused byabrasives and the 0.56 μm and/or 1.01 μm bin size are inadequate atadequately characterizing problematic LPC counts from the non-dissolvingabrasives.

Example 6

In this example the use of filtration was investigated to determine whateffect filtration through a depth filter, a commonly used practice inthe CMP industry, may have on the LPC count of a prior art polishingslurry and the polishing composition of the present disclosure. Theprior art polishing slurry has an LPC count that exceeds the limittaught for polishing compositions according to the present disclosureprior to the filtration. Conversely, the polishing composition of thepresent disclosure has an LPC count below the limit taught for polishingslurries according to the present disclosure prior to the filtration.The components of the two polishing slurries were chemically the sameand used in the same amounts within each composition.

FIG. 13 shows a plot of the LPC counts, using a 0.2 μm bin size,measured over a period of 11 days for the prior art polishingcomposition and the polishing composition of the present disclosureafter they have been subjected to a filtration using a 0.1 μm depthfilter. As the plot shows, the filtration using a 0.1 μm depth filterdoes slightly reduce the LPC counts for both the prior art and thepolishing composition of the present disclosure, but the LPC counts forthe prior art polishing composition never approaches the level obtainedfor the polishing composition of the present disclosure.

Example 7

In this example slurries that are formulated according to the presentapplication and comparative slurries formulated not according to thepresent application have their LPC counts per weight % silica abrasiveused in the slurry compared. Slurries 1-4 and 6 are formulated accordingto the present invention, while slurries 5 and 7-10 are comparativeslurries that were not formulated according to the present invention.While all slurries have slightly different formulations one primarydifference is the specific silica product used in each formulation.Table 1 below summarizes the slurries.

TABLE 1 High Propensity Slurry for Scratching 1 No 2 No 3 No 4 No 5 Yes6 No 7 Yes 8 Yes 9 Yes 10 Yes

FIG. 14 shows the LPCs/weight % silica, measured at a 0.2 μm bin size,for Slurries 1-10 at 0, 3, and 7 days after formulation. Slurries 1-4and 6 use silica abrasive products that result in appropriate levels ofLPCs/weight % silica when measured at the 0.2 μm bin size (i.e., fewerthan 800,000 LPCs/% silica), while slurries 5 and 7-10 use silicaproducts that result in LPCs/weight % silica of greater than 800,000LPCs/weight % silica. Wafers polished with slurries 1-4 and 6 showedfewer scratches than were observed on wafers polished with comparativeslurries 5 and 7-10.

FIG. 15 shows the LPCs/weight % silica, measured at a 0.29 μm bin size,for Slurries 1-10 at 0, 3, and 7 days after formulation. Significantly,the comparative slurries (i.e., slurries 5 and 7-10) on average showlower LPC counts at this bin size than the slurries 1-4 and 6 thatproduce less scratches and are formulated according to the presentdisclosure. This result further demonstrates that LPC counts measured atbin sizes 0.29 μm or larger are not correlated well with slurries thatreduce scratches/defects during polishing.

Example 8

In this example slurries that are formulated according to the presentapplication and comparative slurries formulated not according to thepresent application have their LPC counts per weight % solids (i.e.,abrasive and dissolvable solid components) used in the slurry compared.Slurries 1-4 and 6 are formulated according to the present invention,while slurries 5 and 7-10 are comparative slurries that were notformulated according to the present invention. The slurries used in thisexample are the same as the slurries used in Example 7, but the LPCcounts shown in FIGS. 16-17 are instead normalized to weight % solids.

FIG. 16 shows the LPCs/weight % solids, measured at a 0.2 μm bin size,for Slurries 1-10 at 0, 3, and 7 days after formulation. As mentionedpreviously, Slurries 1-4 and 6 show reduced defects after polishing whencompared with comparative Slurries 5 and 7-10. Thus, based on the datashown in FIG. 16, an LPC/weight % solids value of less than 50,000 wouldbe an effective limit for a slurry to reduce defects/scratches duringpolishing.

FIG. 17 shows the LPCs/weight % solids, measured at a 0.29 μm bin size,for Slurries 1-10 at 0, 3, and 7 days after formulation. As shown, fourof the five lowest LPCs/weight percent solids are actually Slurries 6-9,which are comparative slurries that demonstrate non-acceptable/increasedscratch levels. Thus, LPC counts measured at bin sizes of 0.29 μm orlarger are not correlated well with slurries that reducescratches/defects during polishing.

Although only a few example embodiments have been described in detailabove, those skilled in the art will readily appreciate that manymodifications are possible in the example embodiments without materiallydeparting from this invention. Accordingly, all such modifications areintended to be included within the scope of this disclosure as definedin the following claims.

1. A chemical mechanical polishing composition, comprising: an abrasive;a first removal rate enhancer; and water; wherein the polishingcomposition has a value of less than 800,000 for the relation: largeparticle counts/weight percent abrasive, wherein the large particlecount is the total number of particles larger than 0.2 microns permilliliter of the composition.
 2. The composition of claim 1, whereinthe first removal rate enhancer is selected from the group consisting oforganic acids, and organic acid salts, amino acids, carboxylic acids,polyamines, ammonia based compounds, quaternary ammonium compounds,inorganic acids, compounds with both carboxylic and amino functions,ethylenediaminetetraacetic acid, diethylene triamine pentaacetic acid,and any mixtures thereof.
 3. The composition of claim 1, furthercomprising a corrosion inhibitor selected from the group consisting ofazole and azole derivatives.
 4. The composition of claim 1, furthercomprising an abrasive selected from the group consisting of alumina,fumed silica, colloidal silica, coated particles, titania, ceria,zirconia, and any mixtures thereof.
 5. The composition of claim 4,wherein the abrasive is selected from the group consisting of fumedsilica, colloidal silica, and mixtures thereof.
 6. The composition ofclaim 1, wherein the amount of abrasive in the composition is at least0.05% by weight.
 7. The composition of claim 1, further comprising anoxidizer selected from the group consisting of hydrogen peroxide,ammonium persulfate, silver nitrate, ferric nitrates, ferric chloride,per acid, per salts, ozone water, potassium ferricyanide, potassiumdichromate, potassium iodate, potassium bromate, vanadium trioxide,hypochlorous acid, sodium hypochlorite, potassium hypochlorite, calciumhypochlorite, magnesium hypochlorite, ferric nitrate, KMnO₄, otherinorganic or organic peroxides, and any mixtures thereof.
 8. Thecomposition of claim 1, further comprising at least one selected fromthe group consisting of a surfactant, a second removal rate enhancer, abiocide, a surface finisher, a pH adjuster, a defect reduction agent, adishing reducer, a dynamic surface tension reducer, or any mixturesthereof.
 9. The composition of claim 1, wherein the composition is notfiltered prior to measuring the large particle counts/weight % abrasive,when measured using a 0.2 μm bin size.
 10. The composition of claim 1,where the composition is aged for at least 3 days after formulationprior to measuring the large particle counts/weight % abrasive, whenmeasured using a 0.2 μm bin size.
 11. A chemical mechanical polishingcomposition, comprising: an abrasive; a first removal rate enhancer; andwater; wherein the polishing composition has a value of less than 50,000for the relation: large particle counts/weight percent solids, whereinthe large particle count is the total number of particles larger than0.2 microns per milliliter of the composition.
 12. A method of polishinga substrate, comprising the steps of: applying the composition of claim1 to the substrate; and applying pressure to the substrate with apolishing pad, to remove at least a portion of the surface of thesubstrate.
 13. A method of preparing a polishing composition, whereinthe polishing composition comprises: an abrasive; a first removal rateenhancer; and water; wherein the polishing composition has a value ofless than 800,000 for the relation: large particle counts/weight percentabrasive, wherein the large particle count is the total number ofparticles larger than 0.2 microns per milliliter of the composition,wherein the method comprises the steps of: selecting the abrasive sothat it conforms to the value; and combining the abrasive, the firstremoval rate enhancer, and the water.
 14. The method of claim 13,wherein the abrasive is not filtered before the combining step.
 15. Themethod of claim 14, further comprising the step of chemically treatingthe abrasives so that they conform to the value.
 16. The method of claim13, further comprising the step of forming the abrasives via chemicalsynthesis so that they conform to the value.